Periodic Table (PDF) | Useful Data | Useful Formulas 


An element is a substance which cannot be broken down into simpler component substances. An atom is the smallest possible unit of an element. There are only 90 naturally occurring elements. Each element is conveniently represented by a symbol which denotes a single atom of that element. For example,
H hydrogen O oxygen C carbon
N nitrogen S sulfur Cl chlorine
He helium Al aluminium Cu copper
Note that each symbol always starts with an upper case letter, and that when a second letter is used, it is always written in lower case. These grammatical rules prevent ambiguities when the formulae of compounds are written. For example, CS is clearly made from carbon (C) and sulfur (S) where Cs is caesium. Although you will be given a Periodic Table listing all the elements in every assessment, it is still worth becoming familiar with the elements' names and symbols. They are, after all, the building blocks of all matter.

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